Data storage media are used to store and retrieve large amounts of digitally encoded data in a fast and efficient manner. Such media have been commercially provided in a number of different forms, such as magnetic, optical and solid-state (e.g., flash memory, etc.).
Of particular interest are optical discs, which store data in a form that can be optically transduced in a readback system. Due to their portability, high data storage capabilities, and relative resistance to damage during handling, optical discs largely remain the worldwide medium of choice to provide and distribute video, audio, software (business, games, etc.), and other types of content.
Optical discs can be provided in a variety of formats, such as compact disc (CD), digital versatile disc (DVD), high density DVD, Blu-Ray, hybrid, mini-disc, etc. Optical discs can also be pre-recorded or recordable by the end user (once or many times), which further enhances the versatility of the media across a number of different markets.
The relative ease with which the content of a particular optical disc can be replicated, however, also constitutes one of the larger issues facing the industry; namely, the protection of intellectual property rights in the content stored on the disc. Along these lines, a number of efforts have been taken to copy protect discs so that unauthorized copying of the contents is prevented, or at least reduced.
Some content providers have desired the ability to append additional information to an optical disc (or other medium) after manufacturing, for copy protection or other purposes. Such information might include a unique serial number, a customer ID, updated files for the pre-recorded data on the disc, etc.
To this end, hybrid optical discs have been proposed with both pre-recorded and recordable portions. The “base” content is stored to the pre-recorded portion during disc manufacturing, and the “new” content is recorded to the recordable portion(s) of the disc at a later time.
Hybrid optical discs often utilize well-known multi-session recording techniques (see e.g., ISO 9660/13490, etc.) to control the writing of data over multiple sessions. For example, the base content is written during a first session, and new data are added to the disc during subsequent recording sessions using a recorder or similar equipment. Such multi-session techniques are also typically used on “regular” (non-hybrid) recordable discs when multiple recording sessions are made.
While a variety of multi-session techniques have been proposed, one commonly employed approach involves recording each session as a new track on the disc. Each new track generally includes an updated copy of the disc file system used to identify the file structure of the disc. Depending on the format, readback systems are generally instructed to find the last (and hence, most up to date) copy of the file system on the disc, and ignore the other, older copies.
Accordingly, with the continued worldwide commercial interest in providing content on optical discs and other types of storage media, there remains a continued need for improvements in the manner in which the content is arranged and identified on the medium. It is to these and other improvements that the present invention is generally directed.